Contributing meaningfully to the alarm-sounding of Mary Pipher's Reviving Ophelia, Brumberg (Fasting Girls: A History of Anorexia Nervosa) examines-- through the lens of the adolescent female body--the crisis of confidence faced by girls in today's hypersexualized consumer culture. From the sanitizing and commercializing of menstruation to the rise of dermatologists, training bras and anorexia nervosa, the changing ways in which girls' bodies have developed over this century--and society's changing attitudes about that development--are sketched vividly and with candor. The average age at menarche is now 12, Brumberg explains. In the 1800s, menarche usually occurred at 15 or 16, today's average age of first intercourse. This earlier physical maturation is accompanied by a steep increase in autonomy over dress, sexual activity and other areas unthinkable in Victorian times--but, the author makes clear, such accelerated maturity comes at a cost. Brumberg argues forcefully that, rather than facilitating emotional or intellectual maturation, ""contemporary culture exacerbates normal adolescent self-consciousness and encourages precocious sexuality."" In a somewhat jumbled conclusion, she advocates multigenerational dialogue to help girls establish a standard of sexual ethics. Brumberg's meticulous documentation includes copious personal diary accounts from adolescent girls. Photos. (Sept.)